Engineered porosity for stiffness-matched, PBF-LB, Nickel-Titanium mandibular graft fixation plates

• Porous NiTi may reduce stress shielding and concentration in skeletal reconstruction devices. • A stiffness-matching approach is utilized to restore normal in vivo loading trajectories. • Our stiffness-matching approach may prevent fatigue-induced device failure. • Quasi-static bending properties do not differ between the two tested pore geometries. • Orthogonal strut geometry shows increased displacement under bending vs. gyroid strut geometry. Bone graft fixation plates, or osteosynthesis plates, are commonly employed in reconstructive surgery to repair segmental bone defects arising from trauma, pathology, or degenerative conditions. Fixation system failures are often attributed to stress concentration or stress shielding. We hypothesize that a fixation system promoting compressive force across the healing interface, while minimally disrupting physiological loading, may reduce hardware failure and bone resorption, respectively. This study investigates the potential of Nickel-Titanium (NiTi) alloys and engineered porous structures for providing superior mechanical integration, compared to conventional Ti6Al4V systems. Non-personalized NiTi plates, produced by Powder Bed Fusion using Laser Beam (PBF-LB), with varied pore geometries—orthogonal struts and Schoen’s gyroid structures—were evaluated via four-point bending, following ASTM F382 guidelines. Thermo-chemical analysis confirmed the presence of the martensitic phase at both room and physiological temperatures, indicating shape memory behavior. Mechanical testing revealed no significant difference in stiffness between the two pore designs, with elastic moduli ranging from 13 to 22 GPa. Orthogonal geometries exhibited increased deflection after 50,000 bending cycles, suggesting progressive strain accumulation, but neither design failed catastrophically after 1 million cycles. These findings support NiTi fixation plates for systems designed to promote biomechanically favorable healing through stiffness matching and holistic device engagement.